图片放大镜效果，供大家参考，具体内容如下
一难点：不让黄盒子出界
二难点：让大盒子相应移动（比例）
<html lang="en"> <head> <meta charset="UTF-8"> <title>我的放大镜</title> <style> *{ margin: 0; padding: 0; } .box{ margin: 100px; position: relative; } .small{ width: 350px; height: 350px; border: 1px solid #999; position: relative; } .select{ display: none; width: 100px; height: 100px; background: rgba(255,255,0,0.4); position: absolute; left: 0; top: 0; cursor: move; } .big{ display: none; position: absolute; left: 360px; top: 0; width: 450px; height: 450px; border: 1px solid #ccc; overflow: hidden; } .big img{ position: absolute; left: 0; top: 0; } </style> </head> <body> <div> <div> <img src="https://www.jb51.net/images/001.jpg" alt=""> <div></div> </div> <div> <img src="https://www.jb51.net/images/0001.jpg" alt=""> </div> </div> <script> var smallbox = document.getElementById('smallbox'); var bigbox = document.getElementById('bigbox'); var mask = document.getElementById('mask'); var bigImg = bigbox.children[0]; smallbox.onmouseover = function(){ mask.style.display = "block"; bigbox.style.display = "block"; } smallbox.onmouseout = function(){ mask.style.display = "none"; bigbox.style.display = "none"; } smallbox.onmousemove = function(event){ var event = event || window.event; var x = event.clientX - this.offsetParent.offsetLeft - mask.offsetWidth/2; var y = event.clientY - this.offsetParent.offsetTop - mask.offsetHeight/2; //不让黄盒子出界 if(x < 0){ x = 0; }else if(x > smallbox.offsetWidth - mask.offsetWidth){ x = smallbox.offsetWidth - mask.offsetWidth; } if(y<0) { y = 0; }else if(y > smallbox.offsetHeight - mask.offsetHeight){ y = smallbox.offsetHeight - mask.offsetHeight; } mask.style.left = x + "px"; mask.style.top = y + "px"; bigImg.style.left = -x/smallbox.offsetWidth * bigbox.offsetWidth + "px"; //注意是-x bigImg.style.top = -y/smallbox.offsetHeight * bigbox.offsetHeight + "px"; } </script> </body> </html>